No idea about buying stuff from gta4.
But playing it is great! Loving this game for sure. I just got a ps3 recently, and only have that game right now. Truth be told, theres soo much detail its almost distracting!
I wish they would have raised the view from behind the car while driving. I always hated that in previous versions. I have to hold back slightly on the controller joystick so I can have a decent view over the car... Oh well, driving with the 'in car' view is fun too